(NEXSTAR) — A peaceful Wednesday afternoon in October will be briefly interrupted by blaring alerts on cell phones, TVs and radios as several federal agencies perform a joint test.

The Federal Emergency Management Agency and the Federal Communications Commission — better known as FEMA and the FCC — are running the test of the country’s Emergency Alert System, plus the Wireless Emergency Alert system that goes out to mobile devices.

The test of both systems will take place Wednesday, Oct. 4, at approximately 2:20 p.m. Eastern Time.

At that time, and for 30 minutes after, cell phones that are switched on and within range of a cell phone tower will get a message that reads “THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed.”

Phones that have their settings set to Spanish language by default will get the same message in Spanish.

“To help ensure that these alerts are accessible to the entire public, including people with disabilities, the alerts are accompanied by a unique tone and vibration,” FEMA says.

On television and radio, the test is set to last about one minute, and will look or sound similar to monthly emergency alert system tests you may have heard before. The message will say, “This is a nationwide test of the Emergency Alert System, issued by the Federal Emergency Management Agency, covering the United States from 14:20 to 14:50 hours ET. This is only a test. No action is required by the public.”

If there’s widespread severe weather on Oct. 4, the test will be postponed by one week so it doesn’t create confusion between real emergency alerts and the test.

The October test is the seventh nationwide EAS test for radios and televisions, and the second time all cell phones are being tested.